The invention is in the field of electric lamps having inlead wires provided with bends to shape them into desired configurations for holding a light source such as a filament or arc tube.
U.S. Pat. No. 4,208,603 to Graves and Pikus discloses various types of electric lamps containing inlead wires provided with bends to shape them into desired configurations for holding a light source such as a filament or arc tube. These inlead wires are made from a dispersion-strengthened copper alloy material resulting in wires sufficiently stiff so that they can support the light source without the need for additional support wires. Inlead wires that have been bent to a desired shape, and especially inlead wires made from a stiff and springy material such as the just-mentioned dispersion-strengthed copper alloy, retain a "memory" of their original straight shape and tend to "unbend" or "spring back", in varying degrees, toward the original straight shape. This effect can occur immediately after bending and/or over a period of time. The amount of the spring back is found to be inconsistent among bent inlead wires that have been made identically, this inconsistency being relatively greater for wires of stiffer material.
The aforesaid spring back of bent inlead wires is undesirable because it can cause a lamp's filament to sag or to stretch, and can cause a filament or arc tube to move from its original intended position in a light bulb.